Liquid contact circuit closer



Dec. 8, 1942. W H, :,EFlSCl-iv 2,304,561

LIQUID CONTACT CIRCUIT CLOSER Filed Jan. '7, 1941 Figa i FLM ow xmms/0N 3 GLASS WALTER H. Gramsci-1f BY v v ATTORNEY Patented Dec. 8, 1942 UNITED STATE s PATENToFFIcI-:j-

LIQUID CONTACT CIRCUIT CLOSER I Walter H. Gerisch, NorthBergen, N. J.,assignor. to General Electric Company,a Corporation of New York Application January 7, 1941,' SerialNo. 373,440

I1 Ciaims. (c1.20o-152)'Y The present invention relates to liquid-contact circuit closers of the typev having an envelope y containing a small quantity of mercury which is arranged to complete and-interrupt the circuit between the terminals of the circuit closer. The

` invention is particularly concerned with circuit closersofthe typer in which the major portion of the envelope is constituted of two terminalforming parts which are joined peripherally by a body of glass and which are separated within the envelope by an apertured cermaic barrier adapt-" ed to perform a circuit-interrupting function.

tinuous contact with the outerv periphery of the diaphragm 4.

When the circuit closers of Figs. 1 to 5, inclusive, are rotated about the axis of Symmetry'of the terminals a few degrees from the position illustrated, theopening 5 is raised clear of the mercury, and the circuit between the terminals is broken by separation of the-'mercury within the opening as it flows from each end thereof. In this position. the diaphragm separates the mercury into two pools.A When the circuit closer lsreturned to the position illustratedthe circuit y It is a primary,r object of the invention to proprovements in the structure and composition of the circuit-interrupting barriers employed.

For a consideration of what I believe to bev novel and myinvention, attention is directed tov the accompanying description andthe claims appended thereto. f

In the accompanying drawing:

Fig. 1 is a sectional elevation of a liquid contact circuit closer embodying my invention;

Fig. 2 is a sectional viewtaken on line 2-2 of Fig. 1;

Fig. 3 is a sectional elevation'of a'modicatlon;

Fig. y4 is a sectional view on line 4-4 of Fig. 3;

Fig. 5 isa sectional elevation of another Inodication, and i Figs. 6 and 'l are vsectional views of a still `further modication.

Each of the circuit closers illustrated in Figs.

1 to 6, inclusive, has an envelope I containing a limited quantity of mercury 2. The major portion of the envelope comprises opposed straight- When the said circuit closers are in the I between the terminals is completed by the joining of Amercury flowing into the opening 5 from each end thereof. l f v It is not necessary in all cases that' the circuit closersshall be rotated' about the axis ofV symvmetry of the terminals as described in connection with Figs. 1 to 5. In `some cases, it is advantageous that the break in themercury' shall be brought about by tilting the circuit closer as shown in Figs. 6 and 7, in which event the opening 5 is preferably located at the center of the diaphragm,- and sufiicient mercury is provided to insure the closing of the circuit when the circuit closer is in an upright position. With the `circuit I closer in the position shown in Fig. 6, tilting the `drawn cup-shaped metal terminals 3 juxtaposed n The members 3, 3 are hercircuit closer to the left, for example a few degrees from the vertical, as shown inFig. 7, causes the mercury above the right hand edge of the opening 5 to flow to the opposite side of the diaphragm, the portion kof the mercury on the side of the barrier below the said edge being retained there, and the circuitbetweenlthe terminals is broken by separation ofthe mercury at the said edge as it flows from the opening 5. In this position, the diaphragm separates the mercury into two pools. Whenthe circuit closer is returned tothe'position illustrated in Fig. 6, the circuit between the terminals is completed `by the joining of the said mercury pools by the mercury owing back into the opening 5.

A charge ofhydrogen ranging in pressure from about 1 atmosphere to much higher pressures v may advantageously be employed in connection with a switch such as that illustrated. Such hy-l drogen may be introduced into the switch during the manufacturing process through an opening 1, provided in the metal member 3. This opening 1 is thereafter sealed, preferaby by fusion welding a closure member 8 therein, for example,

eflicient above yl4 l0*6. i .stantial quantity of borosilicate. glass may be closing envelope be completely gas tight, In a construction such as that shown in Fig.v l, the fulfillment of this condition is complicated by the fact that the glass closure element 6 must be capable of sealing'not only to the metal terminals 3 but also to the ceramic barrier 4. The successful matching of these diverse elements is a matter of considerable difficulty.

In circuit closers of this type heretofore commercially available good results have been btained by forming the metal parts 3 of'a chrome iron alloy and the glass sealing ring 6 of a relatively high expansion glass-capable of sealing to such an alloy. In this latter connection it has proven desirable to use a lead glass having an expansivity on the order of 9. 10-.6 centimeters per centimeter per degree centigrade, this expansivity being provided, for example, 'by a glass ciently match the sealingv glassk to, avoid producing excessivestrains in itit has beenfound ex- ,pedientr toy form it of. magnesia (a material of veryhigh expansivity)` in combination with a vitreous bonding substance, suchas clay, which ischaracterizedby low expansivity, the materials being admixedin proportions calculated to. reduce the expansivity of the composition vas `a Whole to a value `commensurate with thatof .the sealing glass. Barriers o f thistype are described and claimed lin Louis Navias Patent 52,153,000issued April 4,19 39. .1

Circuit closersof theconstruction just specified have functioned successfully in `practice and have been sold extensively for lowcurrent use`- In attempting to `extend their application to high current circuits,y however, certain difficulties are encountered.- In particular it is found that there is a tendency for excessive erosion ofl the ceramic barrier to occurifthe circuit closer is used to control currents greater than `a few amperes.

, In accordance with the present invention this limitationl is substantially overcome by incorporating'inv the barrier,either superficially or throughout its structure, a quantity of a glass of thejlow expansion borosilicate type, In the lpreferred case a ceramic of the desired quality is prepared by fusing `a mixture of a granular refractory material having a high coefficient of expansionl (e. g. magnesia) and a vitrifiable binder including a substantialamount of` a glass of the above-specified type, the relativelproportions of the combined materialsbeing adjusted to produce a coeicient of expansion of the ceramic as a whole whichis matched to that of the sealing glass by which4 the metallic envelope parts are joined. .i In this connection it is to be noted that while typicalborosilicate glasses have expansion coefficients on the order of 3x10*6 centimeters `per centimeter, magnesiahas an expansion co;

combined with magnesia withoutrproducing a resultant expansivity too low for proper cooperation with `the sealing glass i f In particular I have found that a ceramic hav Consequently, a subtype under consideration requires that the ening a coefficient of expansion suiciently close to that of a lead sealing glass such as Corning 001 may be produced by combining powdered fused magnesia with clay and with a glass of the Pyrex type. For the latter constituent one may use, for example, a borosilicate glass having approximately the following oxide composition:

This is `a typical analysis of the glass sold by the Corning `Glass Company under their code No.

The composition of the ceramic may be varied within limits approximately as follows:

. Per cent Magnesia 65-75 Glass 5-20 Clay Remainderv Y A particular mixture which I have found to have the desired properties consists of Per cent Magnesia 75 Ball clay v l5 No. 774 glass I 10 bling them `for approximately two hours in a ball mill. To render this combination readily moldable one may add a few percent of a temporary binder such, for example, as paraiiin Wax heated to its melting point. The batch is then transferred to a dough mixer and heated to the melting temperature of the wax, whereupon the hot liquid Wax is added to the batch and the mass ,is kneaded until the batch has cooled down to room temperature. Thereafter dry powdered borosiiicate glass of 200 mesh finenessl is added and the batch is further kneaded for 15 or 20 minutes to insure thorough dispersal of the glass powder through the batch. Portions of this composition may be placed in molds of desired shape and size` and exposed to a suflicient degree of jpress'ure to assure a compactly molded product.

'I'heerafter the molded articles are red at a temperature of between 1100 and 1200 C, (preferably about 1150o C.) to remove the temporary binder and to vitrify and fuse the clay and glass metal parts of the device are joined, this result being aconsequence of the correlation of the expansivity of the ceramic with the corresponding property of the sealing glass. In addition, due to the presence of the borosilicate glass component, such barriers are highly resistant to heat shock and to -the erosive action of arcs formed during circuit making and breaking operations. The improvement in this latter respect over otherwise'simil'ar barriers `in which the glass conkstituent is omitted is so 4great as to double the current lwhich maybe interrupted by'ja given form ofbarrier without excessive yerosionof the barrier surfaces. l

The advantages realized from the use -of fthe improved ceramic compositions `speciiied in the v kregion "between the barrier opening and theimost nearly adjacent portion of the envelope wall.

l Such a shoulder, which is'exemplied in Fig.` 1 1 as a continuous `ange Il, is preferably formed so that its inner surface in they region between the barrier opening and the most' nearly adjacent part ofthe envelope wall comprises a rectilinear extension of the surface by which such opening is internally bounded. As so formed, its 4utility is considered to be due to the fact that it serves to prevent the arc formed during acircuitmaking or breaking operation from becoming 'terminally attached to the envelope wall near the glass-to-metal seal, thus creating a danger of cracking the seal. Furthermore, the combina'- tion of such a shoulder with the straight-drawn envelope construction shown is found to prevent repetitive attachment of the arc to any particular point on the envelope Wall surface, and for this reason localized overheating and puncturing of the envelope are avoided.

Results generally similar to those described above as being attributable to the incorporation of boro-silicate glass in the ceramic structure may also be obtained by the application of a coating of this glass to the'surface of a barrier 9 which is otherwise constituted principally of -rnagnesia and clay, such a coating being indicated at I0 in Fig. 3. In this embodiment, which is somewhat more diicult to fabricate than that previously described, the glass coating must be extremely thin in order to avoid cracking due to the expansion differences between the glass and the ceramic. However, if a thickness on 'the order of a few mils is employed, there is little tendency for theglass coating to become separated from the ceramic as 'a result of expansion differences, and the erosion-resisting properties of the coated surfaces are very greatly improved, making the structures useful in the arts generally and particularly as electrical insulators. Insulators of-the composition specified are further described and claimed in my copending application Serial No. 423,413, led December 18, 1941. and assigned to the same assignee as the present application. v

In the construction of Figs. 3 and 4 as in that of Fig. 1, the ceramic barrier is advantageously provided with a projecting shoulder adapted to protect the adjacent surfaces of the envelope from the action of rthe arc formed during the use of the circuit closer. In this case, however, the shoulder which is indicated at I2 does not `extend continuously around the circumference of the barrier but is limited'to the particular region zin which the action of the arc tends to be most pronounced.

Fig. 5 illustrates a'further possible modification of the invention; namely, the combined use of a ceramic incorporating a quantity of borosilicate glass as an essential part of the ceramic composition and a coating lI0 of such glass applied to the surface of the ceramic.

' 'By thev use lof the-improvements described in lthe foregoingit yhas Iproven possible to increase the current rating -of a given switch as much as :one yhundred percent above the value previously `considered safe without signiiicantly changing theiover-alldimensins'of the switch. Moreover,

'this has been accomplished lin a. manner which f .doesnot'addappreciably to the cost of the switch or.' increase the difficulties'of its manufacture.

Lwithin the true spirit ing disclosure.

. While-the invention has been described by reference to particular embodiments thereof, it will fbe :understood .that numerous furthermodiiica- 'tions may be `made by thoseV Skilled inthe art withouty :actually .departing from the invention.

YI, therefore, aim in' the appended claims tocover all vsuch yequivalent variations and uses as come and scope of the forego.-

`What'I claim as new and desire to secure by Letters lPat'ent of the United States is:

1.'A oircuitcloserof the tlpewhich comprises a multipart yenclosurepa quantity of a liquidcontact 4medium vwithin the enclosure, a quantity'of sealing'glass of 'relatively high expansivity 'joining the'parts of the enclosure, and an aperture-d circuit-interrupting barrier within the said enclosure and sealed to the said glass, wherein the said barrier consists essentiallyy of a high expansion refractory combined with a low "expansion vitreous bonding material in such proportions as to produce a coeilicient of expansion of the `combination comparable to that of the said scaling glass and in which atleast the circuit-interrupting surfaces of the barrier incorporate glass of the low expansion boro-silicate type.

2. -A circuit closer of the type which comprises a multipart enclosure, a quantity of a liquidcontact medium within the enclosure, a quantity of sealing vglass `of relatively high expansivity joining the parts of the enclosure, and an aperturedcircuit-interrupting barrier within the said enclosure and sealed to the said glass wherein the said barrier-consists essentially of magnesia and a vitreous bonding material containing a substantial proportion of a glass of the low expansion boro-silicate type, the magnesia and bonding material'being combined in such proportions yas to have a coeiiicient ofexpansion -comparable to that of the said sealing glass.

v3. A circuit closer of the type which comprises a multipart enclosure, a quantity of a liquidcontact `medium within the enclosure, a quantity ofsealing glass of relatively high expansivity joiningthe parts of the enclosure, and an apertured lcircuit-interrupting barrier within the said enclosure and sealed to the said glass.

wherein'the said barrier consists essentially of :magnesia and a vitried bonding material including at least 5% of a low expansion borosilicate glass, said magnesia and said bonding material being combined in such proportions as to have a coeiiicient of expansion comparable to thatof the sealing glass.

4. A circuit closer of the type which comprises a multipart enclosure,` a quantity of a liquidcontact vmedium within 'theenclosura a quantityof sealing glass of relatively high expansivity joining .theparts of the. enclosure, and an apertured lcircuit-interrupting barrier within the said enclosure and sealed to the said glass, wherein the said barrier consists essentially of magnesia, clay and a substantial quantity of glass of the low expansion borosilicate type, the magnesia, glass, and clay being combined in such proporof sealing glass of relatively high i enclosure and sealed to the-said glass,

yrup'ting 'surfaces v a thin layer of a glass of the low expansion borojoining the parts of` tured circuit-interrupting barrier within v combined with a low expansion vitreous bonding material in such proportions efficient of expansion comparable to that oi the as to have a cosaid sealing glass and in which the circuit-intersilicate types@v g I v i. l.

l 6. An interrupting element for a liquid-contact circuit closer, saideiement consisting essentially of a high expansion refractory and a low expansion vitreous bonding material including boro-silicate glass covering at least the circuitt interrupting surfaces of the element.

for a liquid-con- 7. An interrupting u element tact circuit'closer, said element .consisting essentially of fused magnesia and a' low expansion vitreous bonding material including' a substanenclosure, a quantityv oi .the barrier are .coated withv rtial proportion of a low expansion borosilicate glass.

8. An interrupting element for a liquid contact circuit-closer, said element consisting essentially of a high expansion refractory in combination with a low expansion vitreous bonding material and having the circuit interrupting surfaces of the, element coated with a thin layer oi low expansion boro-silicate glass.

9. An interruptingvelement for a liquid-contact circuit closer, said element consisting of a fused composition of from 65 to "75% fused magnesia, at least 5% of a low expansion borosilicate glass and a complementary proportion of vclay.

10. An linterrupting element fora liquid-contact circuit closer, said element consisting essentially ofa composition of from 65 to 75% magnesia, from 5 to 20% of Vlow expansion borosilicate glass and a complementary proportion of clay. y

11. An interrupting element for a liquid-contact'circuit closer, said element consisting essentially of about '75% magnesia, and about 10% of a low expansion borosilicate glass.

WALTER H. GERISCH.

about 15% clay. 

